(1) Field of the Invention
This invention relates to organic compounds useful as pesticides. More particularly, it is directed to thermally stabilized carbamate derivatives of oximes having commercial importance as miticides, as nematocides, and especially as insecticides, and to the process for preparing these stabilized compositions.
(2) Description of the Prior Art
An oxime carbamate derivative such as 3,3-dimethyl-2-methylcarbamyloximino-1-methylthiobutane, commonly known as thiofanox (or TFX) has enjoyed increasing success as an effective insecticide. It typically is formuated for commercial application into granular products containing 5, 10 or 15 percent of the oxime carbamate as active ingredient. These products are prepared by impregnating inert granular carrier materials such as Fuller's earth and other clay-like, highly absorptive mineral mixtures, with the oxime carbamate. However, as the chemical is a solid at room temperature, it must be melted prior to application onto the carrier. It becomes highly unstable with warming, oftentimes decomposing significantly.
British patent application No. 2,000,031, published Jan. 4, 1979, in the name of Shell Internationale Research Maatschappij B.V., teaches the use of ethylenediaminetetraacetic acid (EDTA) and/or an alkali metal salt thereof as stabilizer for technical-grade oxime carbamates, said EDTA acid or salt serving to prevent substantial decomposition of the technical-grade materials during warming and formulating. EDTA and/or the alkali metal salt thereof, being only slightly soluble in water, are likewise substantially insoluble in technical-grade oxime carbamate. Thus, they must be slurried into the molten chemical and may settle out to a significant degree when the molten carbamate slowly cools and solidifies. As taught by the aforesaid patent application, generally from 0.5 to 5.0 molar percent and preferably, from 1.0 to 2.0 molar percent of EDTA-containing materials are employed in order to suppress the significant decomposition of said carbamate with warming and formulating.
It has now been found that use of compounds other than EDTA provide equivalent, if not improved stability to technical-grade oxime carbamates during melting thereof, while providing other formulating advantages thereto.